Starling Via is a platform for modular synthesis that consists of a single hardware platform which can be flash programmed for several different modules, each having a different faceplate. The overall architecture is comprised of a digitally-controlled cross-fader, coupled to a versatile ‘contour generator’. The META is one of five modules (at this time) that use the Via platform. Their website has excellent documentation that I don’t need to duplicate here. I bought a DIY kit from Modular Addict. I’m going to describe the build and then go into some detail with demos of four main modes: Envelope Generator, Drum, Oscillator, and Voltage Sequences.

Building the kit

The DIY kit from Modular Addict consists of three items: the PC board, the optional parts kit, and the front panel. Each firmware has an associated panel. Starling provides excellent step-by-step assembly instructions, including videos of each step.

I won’t go into assembly details, since the instructions are easy to follow. The board breaks out into three: Digital board with Eurorack power header, analog board that also holds the panel parts, expander board. After assembly, it looks like this.

Flashing the firmware

Flashing is done through a USB connection to your computer, by a provided software tool called Viaflash. After following the directions for MacOS, the tool ran and detected the board. But it failed to install the firmware, for reasons as yet unexplained. I received a quick response to a support email from Will at Starling. He provided a zip file of the binaries and a MacOS command line to run the flashing. That worked the first time.

The Cross-Fader Concept

Voltage excursions lie at the heart of modular synthesis. A ‘cycle’ consists of the movement of a voltage from some lower bound value to some upper bound value and back again. The rate and shape of these two transition can vary greatly. Slow, non-repeating excursions are typical of ‘envelope’ generators (which really should be called contour generators, because the term ‘envelope’ really means when a contour is applied to a signal amplitude). Repeating cycles are oscillations.

Most envelope generators and oscillators use fixed bounds. Contours for envelopes typically start at zero volts, rise to some maximum fixed value and fall back to zero. Oscillators are typically bipolar. Utility modules, often called polarizers, can be used to vary the amplitude, direction, and offset of any signal. The distinctive idea in the Via line is to make the bounds into controllable parameters. The A and B inputs on META are key to adding great flexibility and more modulation opportunities. Cross-fading between the A & B inputs, by means of a versatile contour generator, is the heart of the design.

Envelope/LFO Modes

In envelope mode, META has five Trigger settings, allowing for AD, A/R, Gated A/R, Reset, and Pendulum, which cover all the possible trigger/gate behaviors associated with envelope generation. There is CV over rise and fall, separately, via the T1 and T2 CV inputs. META takes full advantage of the contour Table of eight shapes, each of which has a variable parameter with CV. Available shapes include linear, logarithmic and exponential curves, as well as ADSR shapes, lumps, and others. An envelope is generated by a fade from the A input to the B input and back. Typically you set A to 0V and B to +5V for a standard envelope. The B level pot allows the A X B output to be attenuated and inverted.

Four Outputs

The Triangle output can be selected to be a linear ramp wave with rise and fall times matching the attack and decay times of the envelope, or it can be the direct output of the contour generator, i.e. the envelope. Its range is fixed between zero and five volts.

The main pulse output can be selected to be high during attack or high during release.

The delta pulse output always indicates the instantaneous direction of the contour. Multiple reversals of direction during the envelope result in multiple pulses generated, for example with Lump shapes.

The A X B output is always the output of the cross-fader. With fixed A and B voltages, this follows the contour generator, but with variable offset and amplitude.

VCA

Replacing the B input with an audio signal results in A X B being a VCA, since the module is cross-fading between zero volts and B. So you don’t need an external VCA to shape sounds. Replace A with audio and you now have a true signal cross-fader with truly flexible contours.

LFO

Cycling Envelope mode is an LFO with the same contour shapes and shape CV. With nothing patched to A or B, low and high bounds can be set for the output. Trigger in hard sync mode affords reset.

Demo

This recording demonstrates the looping EG (LFO) with a standard envelope shape, twiddling the attack and decay times. An external oscillator is patched to B. In the second half of the demo another oscillator is patched to A to demonstrate audio cross-fading.

Drum Mode

Non-cycling audio is a drum mode. Four models are available, selected by the Trigger Mode: Kick, Tom, Pluck, and Tone. The wave shape knob and CV sweep across variants of sounds with each table. T1 knob and T1 CV control frequency, while T2 and T2 CV control the release time of the internal drum envelope. (This envelope is available as one of the Triangle output modes.) Patch an external trigger to Trig input and take output from A X B. Use the A and B knobs to choose a range and amplitude for the voltage output. Patch an oscillator into A or B for awesome drum AM sounds.

Demo

This recording goes through the eight audio tables with a manual sweep of the wave shapes. The second part briefly shows each of the four drum models.

Oscillator Mode

The oscillator frequency range is from 16 Hz to 7.5 KHz. T1 is coarse and T2 is fine frequency control. T1 is a fixed 1 volt/octave CV. T2 CV has an attenuator on the expander for doing standard exponential FM. This is a wave table oscillator with eight banks, each with smooth variations by the shape pot and CV input with attenuator. Use the A and B knobs to choose a range and amplitude for the A X B output. Amplitude modulation can be done by patching an LFO or oscillator into the A or B input.

Demo

This audio demonstration is narrated. We hear each of the eight wave tables being manually swept through the shapes. We also hear several types of FM, the AM via the A input (which the narration erroneous calls a type of FM), using the Freeze input to gate the sound on and off and to do a type of modulation at audio rates, a kind of sync sound. And also we hear hard sync. The FM/AM modulation is done with a sine wave from another oscillator.

Sequence Mode

In the non-cycling Sequence Mode, each trigger received starts a contour with special shapes, selected from the tables and modified by the shape pot and CV. T1 is cycle time, T2 is skew. A and B pots and inputs work as expected.

Demo

This narrated demonstration goes through the eight tables. For each table, a sequence is triggered three times manually. The first is with the shape pot all the way CCW, the second in the middle, and the third with the shape fully CW. The output is used to control both the pitch of a VCO and the cutoff frequency of a filter.

What I haven’t mentioned

Sample and Holds

The A and B inputs each pass through sample and holds, with the sampling being controlled internally, according to the S&H mode. This is useful when using signals patched to these inputs. The online docs have a full description of how these work. I suggest experimentation.

Presets

Via modules include a way to save and restore six preset combinations of Freq, Loop, Trig, S&H, Table, Triangle mode, Pulse mode.

LEDs

The six LEDs provide useful information about the operation of the module. In particular, the four clear ones in the patch bay have a double function. When changing tables or a parameter for Trig, Triangle, Pulse out, etc., the lights cycle through a pattern that indicates which selection is being made. I found this very helpful.

Open Source

Both the hardware and software for the Via platform is open source.

VCV Rack

Via modules have implementations for VCV Rack, if you want to try them out before buying hardware. I don’t use VCV Rack, so I can’t comment.